Mathematical Model for Predicting the Reservoir Performance of Gas Condensate in Multiphase Flow Systems

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Abstract It is today an undoubted fact that the role of gas condensate systems has increased multifold in the global energy chain. However, the development and production of gas condensate systems remains a challenge to the petroleum industry due to its technical complexity. The production data analysis methodologies that has been followed throughout the industry to estimate gas condensate reservoir performance are conventional technologies which have proved ineffective in forecasting and estimating the gas condensate reservoir performance. The complexities involved in the gas condensate system like liquid dropout, condensate blockage and successive multiphase flow of gas and condensate along with the extensive early-transient infinite acting behavior are the root cause for the failure of the gas condensate system.The similarity method transforms the governing PDE for fluid flow into ODE written in terms of single independent variable that combines time and space. The similarity method provides a unique advantage of solving the obtained ODE without the need for linearization. In this paper, the Boltzmann transformation technique is applied to governing equations for multiphase flow for two inner boundary conditions (constant gas flow rate and constant bottomhole pressure) in linear and radial flow regimes. The proposed model is validated by using the line-source solution for single phase gas flow above the dewpoint. The proposed analytical solution for flow above the dewpoint pressure reasonably coincided with the line-source solution for flow above the dewpoint, thus, the proposed methodology can be used as an alternative and less time-consuming approach to predict reservoir performance in early transient multiphase linear and radial flow gas condensate systems. The capillary pressure effects considered in the paper were reasonably negligible considering the fact that a negligible capillary difference was used in fluid PVT properties. But was significant when incorporated as an additional pressure gradient term. This however, demonstrated that capillary pressure effects play a vital role in the production data analysis in gas condensate reservoirs. There is no analytical production analysis method developed to date has considered pressure-saturation as a function of a non-dependent dimensionless coordinate in multiphase (oil, gas and water) linear and radial flow systems. This paper aims to fill this knowledge gap by extending a modification of the similarity method to fully incorporate capillary pressure effect in multiphase linear and radial flow systems in which pressure and saturation are simultaneously considered as functions of a dimensionless coordinate.